Currently, Calibre recognizes both the Calibre library and any mounted devices, but it would be wonderful if we could write plugins that would let Calibre recognize external libraries from which ebooks can be transferred. As a particular example, I'd love to write a plugin that lets Calibre talk to Zotero, so that I can easily pull PDFs of scientific papers onto my Kindle in a way that metadata can be easily provided to the Kindle. I don't know if this has been suggested before, as I am new here and all, so I apologize if I'm reflogging a dead horse.